1. Field of the Invention
The present invention relates to an improved rear fork of a motorcycle equipped with a drive shaft.
2. Description of Background Art
There is a known type rear fork of a motorcycle in which a rear wheel and a gear case are provided in a rear end portion of the rear fork, and in which a drive shaft is provided between an output shaft of a power unit and a gear case. See, for example, Japanese Patent Application Laid-open Publication No. 2006-96274 (FIG. 2).
A motorcycle V shown in FIG. 2 of the above-mentioned document (the reference numerals used in this and the next paragraphs are of the cited document) is a vehicle equipped with a shaft-drive system, which vehicle includes: a vehicle body frame F; a first and a second support blocks 10 and 15, which are respectively attached to a left and a right side portions Fa and Fb of the vehicle body frame F so as to be movable rotationally; a front-end cross member 3, which is attached between the first and the second support blocks 10 and 15; rear-fork pipes 1 and 2, which extend rearward respectively from the first and the second support blocks 10 and 15; and a propeller shaft 7, which is disposed inside the rear-fork pipe 1.
Incidentally, each of the rear-fork pipes 1 and 2 (hereinafter referred to as extending members 1 and 2 respectively) has a closed cross-section structure. The propeller shaft 7 (hereinafter referred to as drive shaft 7) disposed inside the extending member 1 makes the extending members 1 and 2 respectively have cross sections that differ in size from each other. The difference in size of cross section between the extending members 1 and 2 renders the rigidity of the extending member 1 significantly different from that of the extending member 2. This leaves a room for improvement in light of the maneuverability and the like.
An object of the present invention is to provide a motorcycle equipped with a rear fork which has a first and a second extending portions, and a drive shaft passed through the inside of the first extending portion, and in which the rigidities respectively of the first and the second extending portions are approximately the same.